1. Field of the Invention
This invention relates in general to oil well completion equipment, and in particular to an apparatus for preventing loss of fluid in the casing into the formation after perforating.
2. Description of the Prior Art
In one type of well completion, a perforating gun will be secured to a string of tubing and lowered into the casing. A packer will be supported by the string of tubing above the perforating gun. When at the proper depth, the operator will set the packer in the casing. The operator then fires the gun either by increasing hydraulic pressure in the gun from the surface or by dropping a firing bar.
The shaped charges in the perforating gun will penetrate through the casing and annular layer of cement surrounding the casing. The well typically will then be flowed through the tubing for a test. After the test, the perforating gun is retrieved. Once the gun is pulled up through the bore of the packer, fluid contained in the casing above the packer is free to flow down through the bore in the packer.
In some formations, because of low pressure, a considerable amount of the fluid in the casing will flow through the packer into the formation. The penetration of a large amount of well completion fluid into the formation may make it difficult to cause the well to flow formation fluid again.